Community characterization of anaerobic methyltert-butyl ether (MTBE)-degrading enrichment cultures

Abstract

Use of the fuel oxygenate methyl tert-butyl ether (MTBE) has led to widespread environmental contamination. Anaerobic biodegradation of MTBE observed under different redox conditions is a potential means for remediation of contaminated aquifers; however, no responsible microorganisms have been identified as yet. We analyzed the bacterial communities in anaerobic-enriched cultures originating from three different contaminated sediments that have retained MTBE-degrading activity for over a decade. MTBE was transformed to tert-butyl alcohol and the methyl group used as a carbon and energy source. Terminal restriction fragment length polymorphism (T-RFLP) analysis of bacterial 16S rRNA genes showed that the MTBE-utilizing microcosms established from different sediment sources had substantially different community profiles, suggesting that multiple species are capable of MTBE biodegradation. The 16S rRNA genes from one enrichment culture were cloned and sequenced. Phylogenetic analysis showed a diverse community, with phylotypes belonging to the Proteobacteria, Bacteroidetes, Firmicutes, Chloroflexi and Thermotogae. Continued enrichment on MTBE further reduced the community to three predominant phylotypes, as evidenced by T-RFLP analysis, which were most closely related to the Deltaproteobacteria, Firmicutes and Chloroflexi. These three common operational taxonomic units were detectable in the enrichments from Atlantic and Pacific coastal samples. Identification of the microorganisms important in mediating anaerobic MTBE transformation will provide the foundation for developing tools for site assessment and bioremediation monitoring.

Role of back diffusion and biodegradation reactions in sustaining an MTBE/TBA plume in alluvial media

“…If anaerobic biodegradation occurs, MTBE is usually transformed to TBA, which often persists (Somsamak et al, 2006). Acetogenic bacteria, members of methanogenic food webs, are hypothesized to be responsible for ether cleavage of the MTBE molecule and use the released methyl group as a carbon source; however, the pathway and particular organisms responsible are yet to be defined (Youngster et al, 2010a; Youngster et al, 2010b). Field experiments at VAFB have shown that MTBE transforms to TBA under strongly anaerobic conditions induced by experimental ethanol addition (Mackay et al, 2007; McKelvie et al, 2007), with an estimated pseudo-first-order reaction rate constant of 0.046 day −1 (after a lag period of about two months).…”

Anaerobic degradation of a mixture of MtBE, EtBE, TBA, and benzene under different redox conditions

“…MtBE concentrations decreased strongly in all monitoring wells from 2009 to 2015. The detection of TBA in almost all monitoring wells in 2013 indicates that demethylation is the first step in the MtBE biodegradation in the aquifer (Youngster et al 2010 ). Fractionation of stable carbon isotopes of MtBE and TBA in groundwater in 2009 and 2013 confirmed degradation of MtBE.…”

Anaerobic Methyl tert -Butyl Ether-Degrading Microorganisms Identified in Wastewater Treatment Plant Samples by Stable Isotope Probing

“…Kw12) (22.8%) also belonging to the phylum Firmicutes (60). Similarly, following continual enrichment of an anaerobic MTBE-degrading consortium, researchers reduced the community to three dominant phylotypes belonging to Deltaproteobacteria, Chloroflexi, and Firmicutes (67). In addition, Clostridia were found in anaerobic MTBE-degrading consortia under sulfate-and iron-reducing conditions (44).…”

“…The cultures were maintained with anthroquinone-2,6-disulfonate (AQDS), sulfate, or fumarate as electron acceptors, and the authors found that the microbial diversity varied under these different conditions. In another recent study, other researchers characterized the community composition of anaerobic enrichment cultures originating from three different contaminated sediments (67). Interestingly, terminal restriction fragment length polymorphism (TRFLP) profiles indicated substantially different community profiles from MTBE-degrading microcosms established from different sediment sources.…”